1. Designing An Electronic Trigger Mechanism For A Paintball Marker To Allow User Selectable Firing Rates ECE 4884/4007 Fall 2007 Nathan Densmore Matthew Roese Andrew Adams Chris Britton (Team Leader)

2. Overview • Design and implement an electronic trigger • Upgrading is more practical compared to other high end electronic markers • Target customers will be scenario paintball enthusiasts • Principal expense is development cost Georgia Institute of Technology ECE 4007 Fall 2007

3. Design Objectives • Electronic trigger upgrade for the 98 Custom paintball marker • Two firing modes: semi-automatic and fully automatic • LCD screen will display the mode and selected rate of fire • LED indicator for low ammunition and selected firing mode • User friendly up/down buttons to select the rate of fire Georgia Institute of Technology ECE 4007 Fall 2007

4. Design Approach • Key component is PIC Microcontroller (16F690) • Powered by 9V battery • Trigger pressed will activate the micro switch allowing 9V signal to energize the solenoid • PIC will output to an LED indicating firing mode • PIC will output to LCD module indicating firing mode and rate Georgia Institute of Technology ECE 4007 Fall 2007

5. Top Level Design of Circuit Components Georgia Institute of Technology ECE 4007 Fall 2007

6. PIC Controller • 20 pins – 1 VDD, 1 VSS, up to 18 I/O pins • Operates on 2.0-5.5V • Up to 20MHz oscillator/clock • Up to 200ns instruction cycle • 8-bit and 16-bit timer/counters • FLASH/EEPROM – up to 100,000 writes Georgia Institute of Technology ECE 4007 Fall 2007

7. Georgia Institute of Technology ECE 4007 Fall 2007

8. PIC Programming Environment • MPLAB Integrated Development Environment (IDE) included as tool to program PIC • MPLAB is programmed in assembly language • PIC Kit 2 software responsible for debugging code and loading chip Georgia Institute of Technology ECE 4007 Fall 2007

9. Pseudo-code Example Set BPS default; Set Ball Count; When ROF switch  Semi or Full LED if Semi ROF  GREEN Solid if Semi ROF  RED Solid LCD if Semi ROF  Display “Semi” if Full ROF  Diplay “Full” and BPS PUSHBTN if Full ROF  when UP PUSHBTN  BPS + = 1 when DOWN PUSHBTN  BPS - = 1 when UP & DOWN  BPS = 0, Go to LED, LCD Georgia Institute of Technology ECE 4007 Fall 2007

10. Power Supply Schematic Georgia Institute of Technology ECE 4007 Fall 2007

11. Debounced Trigger Circuit • “Beginning” of circuit, and activated when trigger is pulled • Switch will send a high input to the PIC controller Georgia Institute of Technology ECE 4007 Fall 2007

12. Push Buttons (Up/Down) • UP and DOWN pushbuttons are inputs to the PIC; used only when in Full Auto Mode • UP pushbutton will increase firing rate; DOWN will decrease firing rate • Both UP and DOWN selected simultaneously will RESET ball count Georgia Institute of Technology ECE 4007 Fall 2007

13. LED Mode Indicator • Semi Mode: Green LED • Full Mode: Red LED • Low Ammo Status: LED alternates red and green Georgia Institute of Technology ECE 4007 Fall 2007

14. LCD Module • Display numbers and words • More versatile than 7- segment LED • Line length 8 characters • 14 pins in order to interface PIC controller • 8 data lines, 3 control lines, & 2 power lines • Time delay between LCD and PIC interface Georgia Institute of Technology ECE 4007 Fall 2007

15. Solenoid • Powered by +9V • PIC outputs +5V and closes transistor circuit • Current freely flows and fires the solenoid • PIC outputs 0V and opens transistor circuit • Current stops flowing and solenoid returns to initial state • Diode prevents residual current from damaging transistor Georgia Institute of Technology ECE 4007 Fall 2007

16. Mechanical Operation • Operator pulls trigger • Trigger throws trigger switch • Solenoid fires and forces rod upward • Rod rotates sear rocker pin and releases bolt • Bolt spring sends bolt forward inducing firing operation • Blowback resets bolt, locking sear into initial position • Solenoid magnet resets solenoid to initial position Georgia Institute of Technology ECE 4007 Fall 2007

17. Component Enclosure • Plastic enclosure will mount on marker’s magazine • Enclosure will house all of the electronic trigger assembly Georgia Institute of Technology ECE 4007 Fall 2007

18. Technical Advantages and Disadvantages • LCD module is more flexible than 7-segment LED display • Relatively inexpensive production cost • Circuit components are easily replaceable98 • Circuit design larger than existing products • LCD module is bulky Georgia Institute of Technology ECE 4007 Fall 2007

19. Marketing Advantages • Ability to change firing modes quickly • Able to change rate of fire efficiently • Easy operator interface allows for quick selection of system configurations • LCD data display • No special tool or manual to switch modes or firing rates Georgia Institute of Technology ECE 4007 Fall 2007

20. Cost Analysis Georgia Institute of Technology ECE 4007 Fall 2007

21. Future Work • Program the PIC microcontroller to fire paintball marker (2 weeks) • Design an etched circuit board for more efficient production (1 week) • Program PIC microcontroller to work with LCD module (4 days) • Assemble product and test on marker (3 days) Georgia Institute of Technology ECE 4007 Fall 2007